Centrifugal fans are often used for generating a cooling airflow for internal combustion engines, particularly in such engines for use in lawn mowers. In some cases, these engines may operate in an environment where airborne contaminants such as dust, grass, or gratings may interfere with the operation or performance of the centrifugal fan. Stationary screens or filters may be employed to inhibit contaminants from being drawn into the centrifugal fan, but these screens or filters may become clogged and require frequent cleaning.
Such stationary screens are designed as an inadvertent cover for keeping an operator's extremities from contacting the rotating screen and/or centrifugal fan. Typically, some airborne contaminants pass through the stationary screen, which can clog a rotating screen if used. This requires that the stationary screen to be removed to clean the airborne contaminants from the rotating screen.